The Mars Volta were on Letterman, so DT wouldn't be out of the question.
Only because "The Widow" had massive radio play.
They didn't play "The Widow", and this was on the Bedlam in Goliath supporting tour anyway, so I doubt that particular single had anything to do with it.
But I hope this thing gets off the ground. I'd love to see DT on Conan one day, and it's a great target to shoot for: not as huge and prog-averse as Leno and Letterman, but not as comparatively small as Fallon, Lopez, etc. Anyway, as for the campaign, do the people who've, say, liked the Facebook page actually support the campaign in any way? I actually liked the page a long time ago (back when I was a lurker) and forgot about it. Not much for a guy to do to personally get DT on Conan.
EDIT: Also, what would they play? DT doesn't do the late-night scene, and have they ever actually performed a radio edit of a song?